Such rotary tools serve for the machining of a material. When specific materials or processing methods are used, an additional supply of coolant and/or lubricant is additionally necessary, or at least advantageous. For this purpose, the coolant channels, by means of which a lubricant can also generally be conveyed, are formed into the rotary tool such that exit openings result at suitable locations. Exit openings of the coolant channels may be arranged at the end surface or in chip flutes of the rotary tool, for example.
From U.S. Pat. No. 6,045,301 B, a drill can be gleaned which has helical chip flutes and helical coolant channels. To generate exit openings in the chip flutes, the coolant channels are tapped via radial bores. This requires an additional drilling step to generate the exit openings in the chip flutes.
Similarly, in EP 1 941 960 A1 bores that are transverse to coolant channels extending in a longitudinal direction are additionally formed into a drilling tool, such that these bores are each operatively connected to a coolant channel. As a result, coolant channels that each have multiple exit openings are realized. For example, an embodiment is disclosed having two coolant channels that each open into a lateral exit opening and an exit opening at an end surface. Here as well, additional process steps are disadvantageously necessary, in particular drilling on curved surfaces to fashion different exit openings.
Furthermore, in US 2006/0204345 A1 a drill is disclosed which is fluted straight over a majority of the cutting part, and accordingly also has coolant channels running in straight lines. The chip flutes are designed to be spiral shaped only in an end-surface portion. Due to the spiral-shaped course of the chip flutes, the coolant channels running in straight lines in this end-surface portion are cut by the chip flutes to form exit openings. The exit openings can be fashioned only in the chip flutes in this case. Furthermore, the chip flutes must be executed in straight lines in a sufficiently long portion, whereby in particular their chip-conveying properties and the stability of the drilling tool are negatively affected.
A rotary tool in the form of a drill is furthermore disclosed in US 2010/0150673 A1, for example. The principle disclosed there is approximately the opposite principle in comparison with that described in US 2006/0204345A1. Namely, the drill has chip flutes and coolant channels running in a spiral shape in the rear region of the cutting part, and in the front region a portion is fashioned in which only the coolant channels are not spiral-shaped, meaning they run in straight lines. The coolant channels are hereby cut by the spirally continuing chip flutes as well. In this way, exit openings of the coolant channels are achieved in the chip flutes.
However, the associated production method is complicated. In the process, a number of coolant channels are drilled into a blank extending in a longitudinal direction, such that these coolant channels each extend in straight lines and parallel to one another in the longitudinal direction. The blank is subsequently clamped at two points along the longitudinal axis and twisted about the longitudinal axis, whereby the coolant channels are transformed into a helix shape. The points are selected such that an unrotated portion with likewise unrotated coolant channels remains at the end face. A number of chip flutes are subsequently milled into the blank. A number of ribs in which the coolant channels run remain between the chip flutes. However, the chip flutes are also continued in a spiral on the unrotated portion, whereby the coolant channels present in straight lines on this portion are cut such that exit openings are fashioned in the chip flutes. A disadvantage of this is the high production cost since the blank must in particular be rotated at a first portion but must remain straight on a second portion.